Container having inhibitor composition on its interior



CONTAINER HAVING ENHIBITOR COMPOSITION N ITS INTERIOR Charles Lloyd Muehling and Wesley A. Tarwid, Barrington, 111., assignors to American Can Company, New York, N.Y., a corporation of New Jersey No Drawing. Application July 8, 1958 Serial No. 747,112

'12 Claims. (Cl. 220-64) The present invention pertains to an oxidation or corrosion inhibiting composition and in particular to such a composition having particular utility with canned comestibles.

in certain canned food products such as carbonated beverages and certain fruit juices, the nature of these products causes attack and corrosion of the metal of the can.

Therefore, an object of the present invention is to provide a metal food container so constructed to inhibit interior oxidation after being packed with a product.

An additional object is to provide a metal can having an oxidation inhibitor carried on its interior surface.

Yet another object is to provide a metal can having an oxidation inhibitor on its surface which is readily available to and soluble in a product packed in the can.

Still a further object is to provide a metal can more resistant to an acidic product packed therein by virtue of an oxidation inhibiting composition carried on the interior surface of the can.

Numerous other Objects and advantages of the invention will be apparent as it is better understood from the following description which is of a preferred embodirnent thereof.

The above objects are accomplished by providing an oxidation or corrosion inhibiting composition comprising cysteine or the acid addition salts thereof and a stannous salt; which composition, by means of a water soluble binder, is adhered to some portion of the interior of a metal can whereby the inhibiting composition is available to and dissolves in an aqueous product packed in the can.

For use in the composition of the subject invention, cysteine may be used as the free base, i.e. with the primary amino group thereof unsubstituted; or it may be used as the acid addition salt, that is with an acid attached to its primary amino group. Examples of such operative acid addition salts are the mineral acid addition salts such as hydro-halide, e.g. hydrochloride, the phosphate or phosphoric addition salt, the sulfate or sulfuric acid addition salt; and the organic acid addition salts such as citrate, tartrate, lactate, etc.

Cysteine and its acid salts by themselves provide an oxidation inhibiting function. However, cysteine and its acid salts are relatively unstable compounds which, under the proper conditions, readily alter their molecular structure with the formation of cysteine as a reaction product. Cysteine, according to tests appears to be an oxidation accelerator and as such not only would not perform the function desired in the present invention, but actually would produce just the opposite effect.

It has been discovered that the instability of either cysteine or its acid addition salts described above, are overcome by associating wth the cysteine or its derivative, a stannous salt. The combination of a stannous salt with the cysteine or its acid salts stabilizes these compounds against alteration to the undesirable cystine and other possible reaction products. Completely unexice pectedly, the stannous salt apparently has a synergistic action regarding the oxidation inhibiting function of the cysteine and its acid addition salt whereby the combination of the cysteine or derivatives and stannous salt provides greater oxidation inhibition than the cysteine or its salt alone.

Any stannous salt may be combined with cysteine or its acid addition salt to provide an oxidation inhibiting composition. Although not wishing to be bound by any particular theory, it is believed that it is the stannous ion and not the anionic group attached thereto that provides the desired stabilizing and synergistic function. For the utility disclosed herein, i.e. use with an aqueous or water containing comestible, the stannous salt must be tasteand-odor-free and non-toxic. Among such stannous salts useful are stannous halides, such as stannous chloride, and stannous sulfate, the stannous sulfate being preferred.

For use in the present invention, the cysteine or salt thereof may be combined with the stannous salt in relatively wide ratios, i.e. a mol ratio of 0.1/2 to 10/1 and preferably a mol ratio of 1/1 respectively. p The composition of the instant invention has found wide utility as an oxidation inhibitor within a packed and sealed sheet metal can. To provide the interior of the can with the desired oxidation inhibition, the composition is applied to some interior surface of the can preferably an end. The composition may be applied in any desired design such as a spot on the body or end, preferably in the center of the latter; or as an annular ring on or adjacent to the countersink wall of the end. Neither of the ingredients, i.e. the cysteine material or the stannous salt, of the oxidation inhibiting composition has film forming properties or is particularly adherent to a given surface. Therefore, to attach or adhere this composition to some portion of the interior of the can, it is necessary that the oxidation inhibiting composition be incorporated into a vehicle. This vehicle must have the property of adherence to the interior surface of the can in the form of a water soluble film. Water solubility of the vehicle or binder is necessary to enable the product packed in the can to dissolve the film and thereby release the oxidation inhibiting composition into the product where it performs its desired function. This film also should not appreciably alter the appearance of the inside of the can, e.g. it should not be highly colored. Further, since one use of the material is with food products, the vehicle or binder must be non-toxic and substantially taste and odor free.

Any material having the above described properties is operable in the present invention. Examples of binders which have been tested are polyvinyl alcohol, carboxymethyl cellulose, polyvinyl pyrollidone, polyvinyl methylether, gelatine, dextrine, methyl cellulose and solid polyethylene glycols. For certain purposes, it may be desirable to use combinations of two or more of these binders. For use in the instant invention, a combination of methyl cellulose and solid polyethylene glycol is preferred.

For application to some portion of the interior of the can, the solid ingredients; i.e. the cysteine material, the stannous salt, and the vehicle therefor; are dissolved in water. The viscosity of the liquid composition is adjusted to a desired level governed by the particular application employed; this adjustment being made by varying the ratio of solids to water. Most usually, adjustment of viscosity is accomplished by varying the amount of film former or binder since the amount of inhibitor is governed by the particular oxidation or corrosion inhibiting action to be achieved and the product packed in the can. For example, to prevent corrosion of the metal can by a carbonated beverage packed in the can, from 1 to 50 parts per million of the inhibiting composition is generally used. Since the vehicle is innocuous v 3 to the product, i.e. non-toxic and taste free, quantities thereof can be varied over relatively wide limits without producing any undesirable effect.

A predetermined amount of the aqueous solution is then deposited on some portion of the interior of the can; preferably on an end of the can. The thus coated member is then heated to evaporate the water and leave behind on the can part a solid, substantially invisible film comprising the inhibitor composition and binder". There- 'after, the can is filled with product and hermetically sealed. In the normal handling of the canned product, it is given suflicient agitation so that the product washes against all interior surfaces of the can whereby the binder film holding the inhibitor composition onto the can surface is dissolved and released into the product.

It is thought that the invention and many of its attendant advantages will be understood from the foregoing 2. A sheet metal can having adhered to at least a portion of its interior surface by means of a Water soluble said said

a compound is cysteine.

a stannous salt and a compound selected from the group V, V

cysteine and the acid addition salts thereof.

7. The metal can set forth in claim 2 wherein compound is cysteine sulfate.

8. The metal can set forth "in claim compoundis cysteine phosphate.

9. The metal can set forth in claim 2 wherein composition is adhered to an end of said can.

10. The metal can set forth in'claim 9 wherein composition is adhered to the top end of said can.

11. The metal can set forth in claim 2 wherein compound and said stannous salt are present in a ratio of 0.5/1 to 4/1 respectively.

12. The metal can set forth in claim 11 wherein mol ratio is l to 1.

said

2 wherein said said said

said

said

No references cited.

mol

UNlTED STATES PATENT OFFICE CERTIFICATE 0F CORRECTIGN 1 November 24., 19

Chmies Lloyd Muehling" at 9,1,

It is herebj certified that error appears in the-printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

q D, 's-ad cysmne me '03, 1.0?

Signed. and

Attest:

ROBERT C. WATSON lie AXLIXE Commissioner of Patents Attesting Officer UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Eatery; 50,, 2,914,213 November 24, 1959 Charles Lloyd et ale It is hereby certified that error appears in the -printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Colman: 1, ine 61, "cysteine" read eye-tine l ne 62, for *Cysteins" read m Cystine Signed and semen Attest:

KARL H, AXLENE ROBERT C. WATSON Commissioner of Patents Attesting Officer 

1. A CONTAINER AT LEAST A PORTION OF WHICH IS COMPOSED OF METAL HAVING ADHERED TO AT LEAST A PORTION OF ITS INTERIOR SURFACE BY MEANS OF A WATER SOLUBLE EDIBLE FILM FORMER AN OXIDATION INHIBITING COMPOSITION COMPRISING A STANNOUS SALT AND A COMPOUND SELECTED FROM THE GROUP CYSTEINE AND THE ACID ADDITION SALTS THEREOF. 